The invention relates to a filter, in particular for compressed gas and compressed air systems.
Compressed gas systems, in particular compressed air systems require filters to separate solid and liquid foreign matters, for example dirt particles, condensate, and oil, that are carried in the gas flow.
Such filters normally are made of a two-part housing with a top part and a bottom part which are either bolted with one another or connected with one another by means of a coupling nut or a bayonet coupling. The housing top part normally has on diametrically opposite sides an inlet channel and an outlet channel. The inlet channel feeds either in midsection into a hollow-cylindrical filter element arranged in the bottom part or into the annular space between the filter element and the housing of the bottom part. As a result, the outlet channel extends either from the annular space or from the interior of the filter element, depending on whether the flow through the filter element is from inside to the outside or from the outside to the inside. The flow direction in the filter is therefore established after installation and cannot be changed in the installation position. In addition to the flow direction, also the field of application of the filter is established because the flow through the filter element is from outside to inside when dust filtering is involved, and from inside to outside when coalescence filtering for separating compressed air condensate is involved. The majority of conventional filters are thus suitable either exclusively as dust filters or exclusively as coalescence filters, when the flow direction is established after installation into the compressed air system.
DE 103 09 428 B4 discloses a filter having an attachment flange arranged between the top part of the filter and the hollow-cylindrical filter element arranged in the bottom part, with the attachment flange having a feed channel, which is in communication with the filter chamber formed in the interior of the cylindrical filter element, and having a drain channel, which feeds into the annular chamber between the filter element and the bottom part of the housing. By way of a point-symmetric configuration of the filter-element-confronting openings of the inlet and outlet channels in the top part of the filter, the inlet channel or the outlet channel of the filter can be connected with the filter chamber through selective rotation of the attachment flange. As a result, the flow direction of the filter element can be changed through selective rotation of the attachment flange.
When using such filters in a compressed gas or compressed air system, the components of the filter must be sized to withstand the applied pressures. For that reason, the housing parts of the filter are normally manufactured from metal, in particular aluminum. This normally applies also for the top part of the filter (filter head) which has the inlet and outlet channels, as disclosed in the afore-mentioned DE 103 09 428 B4 for example.
The inlet channel as well as also the outlet channel includes in the filter head of DE 103 09 428 B4 a horizontal straight section which connects via a 90° bend into a vertical section. When the filter head is constructed as a milled aluminum component or as a cast aluminum component, such a course of the inlet and outlet channels can be realized in a simple manner by two milled holes which meet within the component. The flow dynamics of such a course of the inlet and outlet channels is however not optimal. In order to optimize the differential pressure, a course that is as even as possible, i.e. in particular without edges and shoulders, and a great length of the channels are desirable.